1. Technical Field
The technology relates to a pneumatic tire and particularly relates to a pneumatic tire having enhanced tire braking performance on ice.
2. Related Art
Tread patterns in which a plurality of sipes is disposed in a tire pattern in order to enhance braking performance on ice of studless tires are known. Also, in recent years, there has been a tendency toward increasing the number of sipes. However, sipe density is increased as a result of increasing the number of sipes, and while this leads to an increase in the number of edges, it also leads to the problems of the overall rigidity of the block declining and braking performance on ice declining.
Therefore, technology has been proposed in which collapsing of portions of a block that are sandwiched by sipes is suppressed and a decline of block rigidity is suppressed by disposing recesses and protrusions within the sipes (see Japanese Patent No. 3180160).
However, an issue still remains because, as wearing of the block progresses, a height of the portions of the block that are sandwiched by the sipes is reduced, and, moreover, rigidity becomes excessive as a result of suppressing the collapsing of the portions of the block by means of the recesses and protrusions.
Additionally, from a perspective of the rigidity of the block, the portions of the block, which are sandwiched by the sipes, located at the edges of the block in the tire width direction are prone to collapse. Moreover, from a perspective of the rigidity of the portions of the block, if a length of the sipes is great, the portions of the block located in a central region in the longitudinal direction will be prone to collapse.
Thus, when there are portions of the block in the longitudinal direction of the sipes that are more prone to collapse compared with other areas, it is difficult to enhance the edge effect.